Assuming you have a drywall ceiling. If you get the taped joints too wet, or scrape too hard at the popcorn, you could end up lifting or even ripping off the joint tape. THEN you'll have a mess.
If it's a plaster ceiling that's just had the popcorn texture applied over it, it's not quite as touchy. However, watch for whatever patch or defect was in the ceiling that made the previous homeowners want to apply the popcorn.
After the ceiling dries out, you can skim coat it with drywall compound. You can buy it pre-mixed in buckets and just apply a very, very light layer to fill in the small voids.
If the voids are larger, you might use spackle, which also comes premixed. It will do a deeper area and dry faster.